The stellar data is a field-reduced subset of HYG v4.1 by David Nash / Astronexus, licensed under Creative Commons Attribution-ShareAlike 4.0 (CC BY-SA 4.0). This derived data retains that licence. Application code is separate.
Modification: visual magnitude at most 3.5, with the Sun excluded. Identity, apparent magnitude, J2000 Cartesian position and velocity are retained. The source commit is 3bf37f4b2d5460e1278286320d1d62fab9b493c1.
Positions are advanced by catalogue space motion, precessed to the mean equator and equinox of date with the P03 equations in USNO Circular 179, and projected above the selected place's geometric horizon using mean sidereal time. UTC approximates UT1; atmospheric visibility, extinction, refraction and nutation are not modelled.
The Panchang uses the approximate browser Sun/Moon calculation. Vara is assigned from the latest estimated local sunrise, using the USNO approximate solar coordinates and the conventional −0.833° centre-altitude threshold. At polar places without a recent sunrise it is unavailable. These are calculation displays, not prediction promises or precision benchmarks.
USNO precession · Sidereal time · Horizon coordinates · Solar model